High-order above-threshold ionization of hydrogen in perturbation theory

Abstract
We describe a very efficient basis-set method for calculating cross sections for high-order above-threshold ionization of a hydrogenic atom in perturbation theory. We present results for up to 20-photon ionization of H(1s) and D(1s) by 1064 nm circularly, linearly, or elliptically polarized radiation. We show the rapid decrease in the integrated cross sections as the polarization passes from linear to circular, and we illustrate the asymmetry in the angular distributions for elliptic polarization.